Maybe I'm insane…

But does anyone else get REALLY annoyed when you strike someone in the head with a power sword and their hair bursts into flames.

Maybe this is just me…but when I have a sword and I hack into someone's neck, I want to be able to scream, "DECAPITATIOOOOOOOON!"

Does anyone else use Impact or Rending damage for power weapons (i.e, impact for thunder hammers and rending for power swords/axes)? 

If critical damage ends up killing an enemy, no matter what the weapon, then my GM simply goes "Okay, you kill him, describe how it happens." It generally involves lots of impaling, throat-slitting, or beheading. If there are any additional effects them we apply it afterwards if it fits.

There was one time I set a would-be mugger on fire with a Hellpistol shot, which caused his ammunition to cook off and explode, killing him and several of his buddies. The last survivor (an Ogryn) took (and failed) a Fear test and ran away screaming. I dusted myself off and walked away. It was glorious.

The same here, my favorite arbites PC has caused so many knee exploding shots with her handcannon and then some brutal shotgun kills. Otherwise they are there to make critical damage, well, noticeable, with effect, as compared to the system of wounds being taken off with no change.